Circuit board



FIG. 1 is a first side view of a circuit board showing my new design;

FIG. 2 is an edge view of the bottom edge of FIG. 1;

FIG. 3 is an edge view of the top edge of FIG. 1;

FIG. 4 is an edge view of either side; and

FIG. 5 is a second side view. 

The ornamental design for a circuit board, as shown. 